The use of progestogens such as Altrenogest is a common practice in swine production that facilitates the introduction of young breeding stock into a group of animals. Progestogen is a hormone that will simulate a pseudo pregnancy in the female and thus block her estrous cycle.
When the treatment is stopped, follicular growth will restart and will lead to the expression of heat high majority in 5 to 7 days after the last dose. As with any hormonal product, it is important to respect the duration of the treatment and the dose administered. The administration of this product must be performed daily at fixed time on pubescent animals and not stimulated by external vectors such as boars or sows in heat. Often perceived as a time-consuming task, the distribution of progestogen when done well allows an optimization of the management of the breeding while creating a positive contact between the breeder and the animals which favors the detection of heat but also the handling of the animals.
The objective of this document is to explain how progestin works and to identify the key factors for successful treatment.
I. Explanation of the estrous cycle of the sow
The estrous cycle of the sow, which lasts 21 days on average, can be divided into 2 phases:
- The luteal phase, which starts after ovulation for 13 to 15 days length, is the period where the corpus luteum is present on the surface of the ovaries and secretes progesterone.
- The follicular phase, which lasts between 4 and 6 days, and corresponds to the growth phase of the pre-ovulatory follicles and leads to the onset of heat and new ovulation.
II. How Altrenogest works
Altrenogest (which is a progesterone analogue) is a molecule of the steroid family used in swine production to facilitate the introduction of sows or young breeding stock put to a breeding group at a specific time.
Its functioning is based on the control of the secretion of GnRH produced by the hypothalamus and of the hormones LH and FSH produced by the pituitary gland as summarized below.
Altrenogest (which is a progesterone analogue) is a molecule of the steroid family used in swine production to facilitate the introduction of sows or young breeding stock put to a breeding group at a specific time.
Its functioning is based on the control of the secretion of GnRH produced by the hypothalamus and of the hormones LH and FSH produced by the pituitary gland as summarized below.
III. The use of altrenogest
Depending on the country, the duration and dosage of treatment may vary. For example, in the USA, 15 mg of altrenogest per sow per day will be given for 14 days, whereas in Europe the daily dose is 20 mg per sow per day for 18 days.
This difference is explained by the American approach considering that the treatment must cover only the luteal phase (from 12 to 13 days) whereas in Europe, the use is based on the respect of a regular cycle of approximately 21 days (18 days of treatment + X days of coming into heat). According to the day of starting, the day is determined in the table below (18 days distribution basis for Europe and 14 days for US (red)):
- Treatment can be started at any time during the cycle.
- Distribute at a fixed time
Considering the rapid availability of the product in the animals system (between 1h and 4h after ingestion) and that the half-life is reached after 14 hours, it is necessary to integrate its distribution as a daily task to be carried out at a fixed time to avoid failures of coming in heat.
- Ensure complete daily dosing
It should be noted that overexposure to the product is without consequence, whereas an underdose is associated with a risk of ovarian development explained by the clipping of the LH peak.
- Precaution for the user: Use gloves when dispensing
Attention: Altrenogest can pass through the skin and is active on men and women (decreased libido, disruption of the menstrual cycle, prolongation of pregnancy, . )
The product can be dispensed either directly into the mouth or into the feed trough. Although the product is very palatable, it is recommended to cover the product with a handful of feed in order to have static animals ingesting the whole product.
IV. The influence of the environment of treated animals
The distribution of the product can be done either directly in the mouth or in the trough. Although the product is very palatable, it is recommended to cover the product with a handful of feed in order to give the animals time to consume the entire product.
- Distribution in the feed trough is to be avoided if there is water in the trough.
- Prefer delivery of altrenogest in the mouth.
For animals housed in groups or in a situation where it is impossible to ensure the quality of individual feeding. This technique requires a learning phase for young animals, which makes it more time-consuming than feeding from the trough. However, the advantage is to create a positive and regular contact between the breeder and the animals, which contributes to facilitate the ease movements when you are in the pen and especially during the detection of heat at the time of inseminations. It is recognized that farms with non-fearful animals are more productive.
- Avoid any stimulation during the distribution phase
Given the effects sought (blocking the cycle via the decrease in FSH and LH secession), in order to avoid “pressing the brake and the gas pedal at the same time”, in breeding farms, the females receiving the treatment must be housed in pens far from that of the boars, or in pens far from its passage. Also in breeding, the females receiving the treatment should be housed in pens far from the boars, or a pen far from its passage. It is also advisable to place treated animals away from contact with weaned females or females in heat.
It is recommended to perform the treatment with altrenogest in a room with multiparous sows (and of course away from boars), in order to facilitate the adaptation of gilts to the microbial environment of the farm.
V. Discontinuation of treatment and reproduction
Although the expression of heat can be obtained without external stimulation, it is advisable to combine the cessation of treatment with normal heat detection practices to promote the expression of estrus and to create uniformity with the time of coming into heat.
- Room transfer
The day after the last distribution, on weaning day, the transfer of gilts to the insemination room and the mixing with weaned sows constitutes a similar stress for the whole group.
The realization of this practice at the time of weaning allows you to apply the same protocols to the entire group (i.e. shower, vitamin, feeding program…) and facilitates the organization of the needed tasks (stimulation, heat detection…).
It is important to note that performing a feeding stress or flushing 2-3 days after stopping the treatment is not useful and may in some cases have negative effects on heat expression or fertility.
- Food stress
For gilts, it is not necessary to limit feed in order to stimulate the onset of heat. If it is done, the limiting must be done the day after the treatment is stopped. One or two meals may be omitted but water should be maintained.
- Boar stimulation
The environment of the sows plays an important role in the stimulation for heat and therefore of the estrous cycle.
The light, the noise, the smells, the contact… are some important parameters produced by the boar. Bi-weekly contact stimulates and promotes the expression of heat and estrus as well as the light (intensity, duration).
It is recommended to have at least 2 boars and to make alternate passages. These boars must be pubescent, sexually active and 1 to 3 years old.
The boar can be introduced to the crated sows or vice versa. In the latter case, the daily movement of the gilts will provide additional positive stimulation.
